Mr. Rosen, who ran his own campaign with volunteers, celebrated at home Tuesday night. Mr. Eddy left a message conceding the race.

Mr. Rosen said he believed his visibility while campaigning made the difference.

"My stand-outs showed people I have perseverance, determination and tenacity," Mr. Rosen said. "I really want to get people involved."

When he takes office in January, Mr. Rosen plans to have neighborhood meetings about Worcester Regional Airport, Coes Pond, crime and the district's schools. He wants residents engaged.

Mr. Rosen thanked Mr. Eddy for his service and credited him for running a good campaign. He wished the contest had featured a debate.

Mr. Eddy, 52, of 3 Barrows Road, said he believed he left a mark on his district during his six years on the council. He had campaigned on his record of preserving neighborhoods, improving quality of life and bolstering the city's Police and Fire departments.

"I am clearly disappointed, but the voters clearly had their say and wanted to go in a different direction," Mr. Eddy said after addressing members of his campaign. "I couldn't have campaigned any harder. There is not a single thing I would have changed in the campaign we ran. I am proud of the campaign I ran. We will move on to another day."

Mr. Rosen of 11 Herbert Road served three terms as an at-large city councilor but did not run in 2009. He was the top vote-getter in the at-large race in 2007 but said "campaign burnout" led to his decision not to run.

Hoping to encourage more city residents to run for elected positions, Mr. Rosen decided to take on Mr. Eddy, who was vying for his fourth term. Mr. Rosen, a retired chemistry teacher, carried solid numbers in his district when he ran at-large in 2007.